Apparatus for treating work pieces

ABSTRACT

An apparatus for treating work pieces in a closed space having a collapsible material. The treatment utilizes a period of subpressure and a period of pressure, in which cavities in the pieces are more or less filled with liquid. Prior to this the cavities are wholly or partially filled with a surface-tension reducing gas and/or solution.

FIELD OF THE INVENTION

The present invention relates to an apparatus for treating a workpiecein a closed spaced in which the workpiece is allowed to rest on asupporting surface intended therefor, and a method of temporarily orpermanently filling the cavities, preferably with the aid of theapparatus defined above, of a material having a bulk density which islower than the material density, said material being subjected to aperiod of subatmospheric pressure or vacuum during which air and/orliquid enclosed in said cavities is removed to a greater or a lesserextent.

Although the invention can be applied within a number of differentfields, it will be described hereinafter with reference to theimpregnation of wood.

DESCRIPTION OF PRIOR ART

It is known to impregnate wood by placing the wood in an autoclave andto subject the wood to a subatmospheric pressure or vacuum treatmentprocess with subsequent pressure treatment, to cause impregnating liquidto be forced into the pores of the wood under pressure. In suchprocesses it is a prime requirement that the impregnating liquid is ableto enter pores which are located deeply within the wood, and a number ofdifferent methods have been proposed to this end. For example, it hasbeen proposed that the pressure to which the liquid and the gas used aresubjected is varied rapidly, in order to provide a good impregnatingeffect, a good stabilising effect and the desired colour effects.Different methods have also been proposed for producing new materials,for example by utilising the aforementioned known methods in conjunctionwith plastics material instead of an impregnating liquid.

OBJECTS OF THE PRESENT INVENTION

An object of the present invention is to utilise an apparatus in whichthe workpiece is allowed to rest on a supporting surface intendedtherefor. For the purpose of enabling a limited amount of impregnatingliquid to be used and for the purpose of obtaining an apparatus whichcomprises light elements, the present invention proposes that for thetreatment of said workpiece there is formed a closed space or chamberwhich comprises or which is defined by a collapsible material. Thecollapsible chamber or material is intended to conform to the outlinesof the workpiece during the subatmospheric pressure treatment process,or during a treatment process in which pressure is supplied to theclosed space from outside.

The present invention also relates to a method of temporarily orpermanently filling cavities in a material whose bulk density is lowerthan its material density, preferably with the aid of an apparatus ofthe type described above. As will be recognized, when the bulk densityof a material is lower than the density of said material, the materialwill contain pores or cavities. Examples of such material include wood,gas-concrete, concrete, etc. The present invention is based on thepreviously known step of subjecting the material to be treated to aperiod of subatmospheric pressure during which air and/or liquidenclosed in the cavities is removed therefrom to a greater or a lesserextent, so that the cavities are able to receive an impregnating liquidor some other liquid which it is desired to supply to said cavities inaccordance with the present method. The basic feature of the methodaccording to the invention resides in the fact that during the pressuretreatment process which follows the period of subatmospheric pressuretreatment, the cavities are filled more or less with liquid. Thepressure period is commenced immediately when the pressure reaches orexceeds atmospheric. In accordance with the invention the cavities arefirst filled totally or partially with a surface-tension reducing gasand/or solution, whereafter said gas and/or solution is or are removedtotally or partially from said cavities.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the invention will be more readily understood and furtherfeatures thereof made apparent, an embodiment thereof will now bedescribed with reference to the accompanying drawings, in which:

FIG. 1 shows a cut-away, shortened horizontal view of an apparatusaccording to the invention,

FIG. 2 shows a side view of the apparatus shown in FIG. 1,

FIG. 3 shows a front view of the apparatus shown in FIGS. 1 and 2showing diagrammatically a lifting device for the closed space, theclosed space being shown partly in cross section,

FIG. 4 shows a diagrammatic vertical sectional view of the apparatusshown in FIGS. 1, 2 and 3 showing the pipes and elements required fortreating or impregnating a workpiece,

FIG. 5 shows, in enlarged scale, a sealing arrangement for use with theembodiment shown in FIG. 1, and

FIG. 6-9 show devices which enable the treatment process to beconcentrated to certain, selected surfaces of said workpiece.

DESCRIPTION OF A PREFERRED EMBODIMENT

In the drawings there is shown an apparatus for treating one or moreworkpieces 1 in a closed space or chamber 2 having aworkpiece-supporting surface 3 which in turn rests on a support surface4. In FIG. 4, the surfaces 3 and 4 are shown displaced from each other.In accordance with the invention, the closed spaced 2 or chamber isdefined by a collapsible material, the portions 2a of which facing thesurface 3 co-act with a frame 5 which is arranged to cooperate with thesurface 3 (see FIG. 5). The frame 5 comprises two angle-irons 5a and 5bwhich are joined together as by welds 5c, 5d to form an inner space 5e.The closed space is defined by a collapsible material in the form of aninner cloth 6, an intermediate layer of, for example, foam plastic 7,and an outer cloth 8.

The portion of the frame 5 facing the surface 3 coacts with a seal 9which is attached to the frame portion 5a and which has lip portions 9aand 9b facing said surface 3, thereby to provide a good seal between theclosed space and the ambient air. This seal is particularly sensitivewhen the workpiece is subjected to a subatmospheric pressure treatmentprocess.

With the illustrated embodiment, there is attached to the frame 5a skirt10 which is arranged to extend into a container located beneath thesurface 3. The purpose of the skirt 10 will be described hereinafter.There is nothing, however, to prevent the skirt 10 from being attacheddirectly to the outer cloth 8 of the collapsible material 2.

An ejector device 11 is connected to the interior of the closed space orchamber 2 via a pipe 12 which is arranged to co-act with a suctiondevice 13. As will be seen from FIG. 4, arranged between the ejector 11and the suction device 13 is a valve 14 and an indicating instrument 15.The suction device 13 is arranged in the upper portion of the space 2and is placed in a corresponding recess in the collapsible material.

The frame 5 supports a number of preferably evenly spaced posts 16 whichsupport a wall extending around the collapsible space 2, said walltogether with the posts 16 and the collapsible material forming aliquid-tight space 17. The space 17 can be filled with liquid by meansof a pipe 18 and a valve 19, thereby to ensure the required pressure onthe seal 9 between the frame 5 and the surface 3. The introduction ofliquid into the space 17 also affords the advantage whereby the airlocated within the closed space 2 and the material is forced out throughthe evacuation pipe 12. The contents of the space 17 can be dischargedto a tank 23 located beneath the surface 3 by means of a pipe 20, avalve 21 and a pipe 22.

In a container 24 there is stored a liquid 25 which is supplied to anejector 11 via a screen 26, a pipe 27 and a pump 28. The used liquid isreturned to the tank 24 via a pipe 30 and a valve 31 to remove air froma space 24a which is separated from space 24b by a wall 32. The airformed in space 24a is removed through a pipe 33.

Gas is stored in a container 34 and is passed to workpiece 1 via pipe35, valve 36, and pipe 37. The pipe 37 extends through frame 5 anddischarges within closed space 2. Treatment liquid 38 can be supplied tothe material via pipe 39, valve 40, pipe 43, valve 42, pipe 41, valve 14and pipe 12. Treatment liquid 25 can be supplied to the space 2 definedby the collapsible material via pipe 27, pump 28, pipe 41, valve 42,pipe 43, valve 44 and pipe 37.

As shown in FIG. 3, the closed space or chamber 2 may be raised andlowered by means of a lifting device 45 comprising ropes 46 and 47 andpulleys 48 and 49. The ropes 46 and 47 may, to advantage, co-act withthe posts 16. The lifting device 45 may be caused to move along guides50 and 51. The lifting device is presumed to comprise known componentsand is not restrictive of the invention and is hence only schematicallydisclosed.

The invention also enables the workpieces to be subjected to aconcentrated and/or partial treatment process. This is illustrated inFIGS. 6-9. For this purpose there is used a porous plate 53 of plasticmaterial which is placed on a workpiece 54 having cells or pores 55. Thecircles shown in the figures together with the dots 55 illustrate thatthe cavities are filled with air. On the material 53 there is placed asheet 56 of irregular shape. During the period of subatmosphericpressure or vacuum treatment the air contained in the cavities 55 isevacuated via the sheet 53 and the recesses 57 in the plate 56,whereupon medium absorbed by the plate 53 under the effect ofatmospheric pressure floats up and temporarily fills the recesses 57.When the pressure returns to normal, the medium returns to the plate 53from which said medium is drawn in the cavities 55 under the effect of apressure below atmospheric, thereby to fill said cavities, as shown inFIG. 9. FIG. 7 shows that the medium in the plate 53 fills the recess 57with liquid and that this liquid during the pressure stage shown in FIG.8 passes through the plate 53 from the space 57 into the pores 55. Thislatter is illustrated in FIG. 9. It will be readily perceived that theapparatus can be provided with several workpiece-supporting surfaces andseveral closed spaces and that these may be used in conjunction with oneanother, depending upon the complexity of the process.

The invention also relates to a method of temporarily or permanentlyfilling cavities in a material whose bulk density is lower than itsmaterial density, with the aid of the above described apparatus. Thematerial is subjected to a subatmospheric pressure or vacuum so as toremove air and/or liquid in the cavities to a greater or a lesserextent. During the subsequent pressure treatment process, the cavitiesare filled to a greater or lesser extent with liquid, there beingobtained during said pressure period an increase in pressure up to orabove atmospheric. By utilising a gas and/or liquid as a surface tensionreducing agent and by permitting said agent to partially or completelyfill the cavities and thereafter to remove, either completely orpartially, said agent from said cavities there is obtained the advantagewhereby a minimum of liquid or impregnating liquid is used, withoutdeparting from the requirement of coating the whole cell wall of thematerial with liquid. Subsequent to first filling the cavities with thegas and/or the solution, it is possible to subject the material to asubatmospheric pressure to a degree such that the gas and/or thesolution boils from the cavities. In this way it is ensured that thecavities are not filled with liquid but that only the cell walls arecoated with liquid. In certain instances it may be expedient to free thematerial from gas and/or solution when said material is surrounded byimpregnating liquid. By increasing and decreasing the pressure rapidly,there is obtained a pumping action which further improves thepossibilities of coating only the cell walls with impregnating liquid.

The cavities may be filled with a readily volatilized hydrocarbon, sucha propylene, the pressure is reduced and the material then lowered intoa less volatile hydrocarbon, such as paraffin (kerosene), tar or thelike, whereupon the lighter hydrocarbon dissolves the heavierhydrocarbon. The stage in the process in which the heavier hydrocarbonis taken up is interrupted by increasing the subatmospheric pressure sothat certain portions of the portion of the heavier hydrocarbon whichhas penetrated the cells is forced out again. By causing the cells to befilled once more, or a number of times, completely or partially withreadily volatilised hydrocarbon, the cell walls become moistened withheavy hydrocarbons without the cells being filled in their entirety.

Although the above description has been made with reference to wood,other porous materials, such as concrete, may also be treated. When thematerial is to be treated with a plastic material, it is expedient tocause the hardener and plastic to be introduced alternatively into thecells. In this latter case considerable reaction heat is obtained, whichis conveniently conducted away by means of a water-spray device.

The skirt 10 shown in FIG. 4 which extends into container 23 in whichliquid 38 is stored is conveniently air-tight, thereby not to jeopardizethe function of the apparatus. Since the evacuation means 11 is anessential part of the invention and since a considerable subatmosphericpressure is required, the liquid pump 11 is preferably operated withwater or aqueous solution which can ensure a subatmospheric pressurewithin the range of a 95-99% vacuum.

If it is assumed that this hydrocarbon is used first and is introducedinto the cells, it is convenient to interrupt the stage in the processin which the heavy hydrocarbons, such as tar, are taken up, thereby toobtain a sealing effect. The saving thus obtained can be enhanced byre-increasing the subatmospheric pressure so that a portion of the tarwhich has penetrated the cells is again forced out and returned to thestorage tank. The cells can then be filled once more, or a number oftimes, with propylene, i.e. the light hydrocarbon, which provides afurther saving since the inner surfaces of the cells are then onlymoistened with the heavier hydrocarbon, such as tar, without the cellsbeing entirely filled.

The feature illustrated in FIGS. 6-9 which enables the treatment processto be concentrated to certain portions of the workpiece can be appliedwhen it is required to fill the cavities of one portion of saidworkpiece with more material than the cavities of other portions of theworkpiece. An example of this is the requirement of filling the cavitiesof the tread surfaces of a stair construction with more plastic materialthan the riser surfaces of said construction. By creating a magazine,for example by permitting soft foam plastic to rest on the surface ofthe material, it is possible to penetrate certain portions of thematerial during the pressure period in certain quantities or excessquantities.

With the illustrated embodiment, the surface 3 is assumed to have theform of a plate having a cloth placed therearound, although it will beunderstood that this construction can be replaced with an air-tight boxdimensioned for subatmospheric pressures. The apparatus can be operatedwith a liquid, such as a 2-4% impregnating solution, or with twodifferent liquids, such as a liquid solution comprising mainly water inthe inner box 24 and, for example, oil, paraffin, plastic, tar solutionor the like in the outer box 23, it being possible to provide the latterwith a pigment for so-called colour impregnation.

With the described embodiment, the surface 3 has the form of a flatplate. However, there is nothing to prevent a recess being formed insaid plate and to arrange for said recess to co-act with a closed spacedefined by a collapsible material, whereby the workpiece can be loweredinto the plate 3, thereby enabling the height dimensions of theillustrated closed space 2 to be reduced. This embodiment can be used toadvantage when, for example, boats or the like are to be impregnated intheir entirety.

Further, in this way the workpiece may comprise fibre plates which areto be impregnated.

This can be effected by placing a bundle of fibre plates into the recessand supplying liquid thereto. Initially all of the plates will float inthe liquid, but as soon as the lowermost plate has absorbed liquid, itwill become heavy and will fall down onto the support surface 3,whereafter the remaining plates in turn also fall onto said surface.

The plates are then subjected to an evacuation step in which the liquidis removed from the plates, whereafter said plates are dried.

What I claim is:
 1. Apparatus for treating workpieces in an enclosedspace, said apparatus comprising:.[.a..]. workpiece-supporting meanshaving a workpiece-supporting surface; .[.b. a rigid framework inproximity to and coextensive with edge portions of saidworkpiece-supporting surface, said framework having a side facing saidworkpiece-supporting surface;.]. .[.c..]. a collapsible material.[.secured to said framework.]. defining an enclosed space over theworkpiece-supporting surface; .[.d. a plurality of spaced posts securedto said framework; and.]. .[.e. wall members secured to and supported bysaid spaced posts extending continuously about said framework, said wallmembers together with said collapsible material defining between them aliquid-tight chamber..]. .Iadd.flexible sealing means between the edgeportions of the workpiece-supporting surface and the side of thecollapsible material facing said edge portions; and a container disposedbeneath said workpiece-supporting surface, said container extendingbeyond the sides of said workpiece-supporting surface, and a skirtmember extending from the collapsible material into said container..Iaddend. .[.
 2. Apparatus in accordance with claim 1 having flexiblesealing means between the edge portions of the workpiece-supportingsurface and the side of the framework facing said edge portions..]..[.3. Apparatus in accordance with claim 1 further comprising acontainer disposed beneath said workpiece-supporting surface, saidcontainer extending beyond the sides of said workpiece-supportingsurface, and a skirt member extending from the framework into saidcontainer..].
 4. Apparatus in accordance with claim .[.3.]. .Iadd.1.Iaddend.wherein the said skirt member is secured to .[.the.]. .Iadd.a.Iaddend.framework .Iadd.disposed between said collapsible material andsaid flexible sealing means.Iaddend..
 5. Apparatus in accordance withclaim .[.3.]. .Iadd.1 .Iaddend.wherein the skirt member is secureddirectly to the collapsible material as an extension therefrom. 6.Apparatus in accordance with claim 1 further comprising ejector meansfor evacuating the enclosed space and pipe means having one endconnected to said ejector means and the end remote from said ejectormeans extending into said enclosed space.
 7. Apparatus in accordancewith claim 6 wherein the end of the pipe means remote from the ejectormeans extends into the upper portion of the enclosed space.
 8. Apparatusin accordance with claim .[.2.]. .Iadd.1 .Iaddend.further comprising.Iadd.means for forming a liquid-tight chamber about said collapsiblematerial and .Iaddend.means for admitting liquid to the liquid-tightchamber whereby to apply pressure to the flexible sealing means and tocause the enclosed space to be evacuated.
 9. Apparatus in accordancewith claim 1 in combination with a soft porous plate having a treatingagent absorbed therein and a perforated plate cooperating with saidporous plate for the concentrated treatment of selected portions of aworkpiece on the workpiece-supporting surface.
 10. Apparatus inaccordance with claim 1 wherein the workpiece-supporting surface isprovided with a recess disposed to coact with an enclosed space definedby the collapsible material.
 11. Apparatus for treating workpieces in anenclosed space, said apparatus comprising:a. workpiece-supporting meanshaving a workpiece-supporting surface; b. a rigid framework in proximityto and coextensive with edge portions of said workpiece-supportingsurface; c. collapsible material secured to said framework defining anenclosed space over said workpiece-supporting surface; d. sealing meansbetween said framework and said workpiece-supporting surface for sealingsaid enclosed space; e. a plurality of spaced posts secured to saidframework; f. wall members secured to and supported by said said spacedposts extending continuously about said framework, said wall memberstogether with said collapsible material defining between them aliquid-tight chamber surrounding said enclosed space; g. suction meansmounted on said collapsible material within the enclosed space; h.external ejector means connected to said suction means for providing asubatmospheric pressure within said enclosed space; i. pressurizingmeans and means connecting said pressurizing means to the enclosed spacefor providing a super-atmospheric pressure within said enclosed space;j. liquid reservoir means; k. liquid transfer means communicating withsaid liquid reservoir means and with said liquid-tight chamber and saidenclosed space; l. valve means connected to said liquid transfer meansfor selectively directing liquid from said reservoir means to saidliquid-tight chamber or to said enclosed space; and m. means forreturning liquid from said liquid-tight chamber and enclosed space tosaid reservoir means.
 12. Apparatus in accordance with claim 11 whereinsaid liquid reservoir means comprises a pair of separate tanks forholding different treating liquids and said liquid transfer meanscomprises (a) separate pipe systems connecting each of said tanks withsaid liquid-tight chamber and said enclosed space, (b) pump meansconnected to said pipe systems for moving liquid from said tanks to saidliquid-tight chamber and enclosed space, and (c) valve means connectedin said pipe systems for selectively directing flow of liquids. 13.Apparatus in accordance with claim 12 wherein the workpiece-supportingmeans is provided with vertical supports, said workpiece-supportingmeans is secured by said vertical supports inside a first of the tanks,and the second of said tanks is mounted under said workpiece-supportingmeans inside said first tank.